Road Warrior: Seasonal formulas for gas affect mileage

EPA approved the use of E15 ethanol, a blend of 85 percent gasoline and 15… (Contributed photo, The…)

March 07, 2013|Dan Hartzell | The Road Warrior

Q: I wonder if you can shed some light on this annoying problem I'm experiencing. During the winter months, I am told by various mechanics that the gasoline industry puts certain additives in our gas that in turn lowers my car's fuel mileage. Why are the oil companies doing this? Are they doing us a favor, or just causing us to use more gas and spend more money? Is this legal?

— Mark Frate, Allentown

A: It's not only legal, Mark, it's a requirement of federal law.

A different chemical cocktail is blended into our gasoline in the hot summer months to help reduce air pollution. Winter-grade gasoline is allowed to be more volatile, or have a greater tendency to evaporate, because the lower prevailing temperature helps control volatility.

Gas stations must be selling exclusively summer-blend gasoline, with its lower volatility limit, by June 1 of each year, according to the Environmental Protection Agency.

The changeover between blends at refineries helps account for some of the increase in gas prices as summer approaches (and again in the fall) as refineries scale back production to adjust equipment for the alternate fuel formulations.

Or so the industry experts say. Some of our more cynical warriors suspect that that's merely an excuse for jacking up prices, or at least, that the industry takes advantage, charging more than the necessary adjustments really cost. As in every other business, I'm sure everyone in the oil game is stepping on the gas to maximize profits. But my intake valves can't accept the implication that Big Oil thoroughly controls pricing. If that were the case, the price at the pump would never take a downhill turn.

Apart from the pricing issue, winter-grade gasoline does yield slightly less energy than the summer blend, Mark, but only by about 1.7 percent on average, according to the EPA. Ethanol's impact is far greater, dropping energy content — and fuel mileage — by more like 30 percent. Still, winter-blend gas imposes its minimal loss on every gallon your engine burns, whereas E10 is a blend of 90 percent gasoline and only 10 percent ethanol, which mitigates ethanol's mileage-lowering quality.

Another reason it's difficult to determine the degree to which seasonal gas formulations affect mileage is that other factors come to play, and with greater impact. An ice-cold engine needs a "richer" gas-air mixture to fire up and idle, and until the engine reaches operating temperature, you're burning more gas compared with startups in the lazy, hazy days of summer. Factors other than winter-blend gas can cut far deeper into mileage — by 20 percent or more — according to the EPA. These include excessive idling (no need to "warm up the engine" in cars made in the last decade or so) and poor road conditions, as well as non-seasonal issues such as lead-foot acceleration, traffic congestion, engine efficiency (need a tuneup?), tire pressure, head winds and hills.

At the end of the road, it's unlikely that winter-blend gas by itself is crimping your mileage in a significant way. You might be able to boost your cold-weather mileage by addressing some of the other matters, or maybe you should try yet another mechanic. Those you've talked to about the problem don't seem up to speed with their fuel facts.

In another fuel-related issue, the EPA approved the use of E15 ethanol, a blend of 85 percent gasoline and 15 percent ethanol, for model-year 2001 and newer cars and light trucks in June 2012, according to AAA, but few E15 gas pumps have taken to the road so far — certainly not in our region. AAA said in December that "a handful" of stations in the Midwest were selling E15, but almost all gasoline sold today consists of E10, or 10 percent ethanol.

Why no E15? Many reasons, according to Jeff Lenard of the National Association of Convenience Stores, which represents the businesses that sell most of our gas these days. Though EPA concluded that E15 won't harm the newer engines, the decision was controversial — AAA wants E15 sales suspended pending further research, and some auto manufacturers have warned that use of E15 could void engine warranties. Ethanol is more corrosive than gasoline, and opponents say it can degrade rubber parts and other engine components.

So gas station owners have obvious liability concerns over possible engine damage, including from "misfueling" — motorists using E15 in older cars, despite EPA rules for specified pump labeling. Lenard said separate and costly new equipment is needed for E15, and there's been no demand in the marketplace for the product. (Quite the contrary, judging by the traffic pulling onto my email deck: Opinions on E15 generally range from wariness to outright hostility.)